Concrete formation involves numerous processes each of which presents unique problems. These processes can include a) placement of the concrete (concrete fall or drop resulting in separation of cement paste from aggregates), b) containment of poured concrete (boundaries limiting concrete flow), c) vibration of the concrete (improper or incomplete consolidation). Inadequacies in one of these processes can lead to formwork failure (from concrete hydraulic pressures) and failure of the connecting components.
The molded and snap-together designs of related art insulated concrete forms (ICF) products restrict the proper positioning and re-positioning of concrete pumping hoses. Numerous and irregularly placed plastic cross-ties, reinforcing steel supports, form hinges, and braces prohibit correct positioning of the concrete pumping hose. The hose is thereby blocked from easy and repetitive entry into the cavity of the forms and is kept at the top of the wall formwork causing the wet concrete mixture to fall a great distance to the bottom of the formwork. This is results in incorrect placement of the wet slurry concrete mix.
During the pour when the wet slurry mix exits the end of the concrete pumping hose, the aggregates, sand and paste in the wet mixture are separated from each other due to impact with these plastic parts or other obstacles. The individual aggregate rocks bounce, spin, and ricochet away from these obstacles separating the cement paste coating from the aggregate's surfaces. The aggregates reaching the bottom of the cavity are no longer properly coated, and the cured concrete's resulting strength at those locations is therefore greatly reduced.
The concrete mix naturally piles up under the end of the pumping hose. Gravity and vibration equipment tends to settle and spread the pile within the space available. The cavity of the related art formwork does not have any effective vertical barriers acting to limit or block the moving concrete. The design of all related art ICF configurations without vertical barriers for containment results in irregular layering, cold joints, and poor and irregular consolidation of the concrete in the interior cavity of the formwork.
Related art insulated concrete form designs also greatly constrict the use and the effectiveness of vibration equipment. Vibration equipment is necessary to consolidate the concrete mixture, remove air pockets, increase the density of the mixture, and improve the strength of the concrete. The related art formwork with its intervening plastic (or non-plastic) parts confounds the use of portable vibration equipment with semi-rigid shafts because the intervening parts crossing and bridging within the formwork restrict the vertical and horizontal movement of the shaft. The vibration equipment has no steering ability to guide the head through the maze of intervening plastic ties, spacers, and fittings. The head and the shaft also catch on the sharp and irregular shapes of the connection parts disrupting attempts at consolidation. Without effective, continuous, and timely vibration, uniform densities and design strengths cannot be achieved. Vibration equipment can only be used when the concrete mixture is contained within formwork and is not flowing or moving.
After an unorganized accumulation of separated aggregate having less paste has reached a depth of a few feet, an attempt at vibration consolidation might be made. The vibrating head is lowered on a semi-rigid shaft into the mixture described above. As soon as the unit is turned on, any amounts of slurry that have enough paste to promote movement will slide away from the vibration equipment and by gravity's effect, slide to a lower void space in the wall cavity. This occurs, to an extent, because there is no effective vertical plane to block the horizontal movement. This modifies the pile of semi-separated slurry to a well separated and semi-leveled position because the portions of the mix having paste will move away from the less paste covered aggregate. Excessive vibration can remove more remaining cement paste from the aggregate. This results in rock and air pockets, honey-combs, and void spaces.
Creating vertical concrete structures has historically required qualified continuous inspection processes to assure compliance with applicable standards. Construction inspection testing efforts of poured-in-place concrete structures are often thwarted because the sample cylinders of liquid concrete taken from the mixing equipment are consolidated separately using testing laboratory methods. Tests for strength are accurate for those test cylinders, but not representative of the areas of poorly consolidated concrete within insulated concrete form (ICF) walls. Vibration consolidation is difficult to regulate in construction work. In large and small scale concrete projects, it is common to use one or two vibrators per concrete pumping hose. The operators of the vibrators follow the hose positions trying to vibrate the varying amounts of accumulated concrete. Because of the required fast pace of concrete placement, due to the high volume of concrete pumping equipment, irregular and incomplete consolidation is a regular occurrence.
Related art insulated concrete forms have limited resistance to the hydraulic pressures of liquid concrete slurry. ICF manufacturers limit the height of the volume of concrete slurry placed because of the likeliness of formwork failure, known as a “blowout.” Field practices must comply with such limitations to avoid the costly complications, delays, and risk of injury due to formwork failure. The concrete is commonly placed at heights recommended at less than four feet, named “lifts” and then given time to harden before more concrete is added on top. The firmer concrete can then support additional lifts of concrete with little fluid pressure on the lower formwork. Due to the necessary delay between lifts, attempts at re-penetration for vibration consolidation of the hardened concrete through the newly placed lift fail regularly. This layering without re-mixing produces a “cold joint” which is incomplete integration of the two lifts. This layering of concrete is unfortunately common and negatively affects the entire project with hidden and continuous cold joints at the intersections of layers.
The related art ICF may have slightly different mechanisms, attachment means, and dimensions, but they all have the same potential failures. During the filling of their product's cavities, the wet concrete mix can and does travel horizontally. The higher the concrete is pumped into one location, the faster it will then flow sideways into a flatter shape. If any vibration is employed on the pile, the greater the distance the liquid concrete can and will flow. This movement prevents any consolidated concrete from staying in one location, and promotes the mixing of consolidated with unconsolidated portions of the mix. Attempting to manage concrete placement, movement, and consolidation from the top of a wall cavity with formwork from the related art is difficult and inefficient.
Some related art ICF products utilize injection molded plastic material placed within the molded expanded polystyrene (EPS) shapes. These products also use tie connectors and experience the problems mentioned previously. Extruded sheet EPS material is now produced with less cost than related art insulated concrete forms. With embodiment of the present invention, EPS sheet material (and other types of wall-formation panels) can now be successfully introduced into the ICF construction industry for applications currently using expensive molded EPS forms with embedded plastic parts.
The purpose of embodiments of the invention is to significantly improve the work product of vertical concrete construction of walls for buildings and other structures by reducing labor and material costs, and better controlling the concrete mix and the resulting product.
Processes described herein utilize known science and physics in a new method of concrete construction that produces the highest quality concrete product possible for the building construction environment. While concrete work has a reputation for limited dimensional accuracy, difficult field work, and intermittent failures, processes disclosed herein greatly improve the finished concrete products, provide easier construction methods and utilize reusable components.
The processes described herein would be utilized in the environment of construction of buildings and other structures. These methods and associated designs will produce concrete assemblies which are highly resistant to damage due to seismic events, hurricane force winds, wild fires, flooding, and impact damage due to flying debris from tornadoes.
Some of the new elements that produce the improvement are the removable, re-useable, arcuate-shaped metal dams and their supporting components. These are positioned vertically in the cavity to be filled with concrete. The dams confine the liquid concrete within particular limits to promote accumulation in a single area allowing the contained concrete to be correctly consolidated with vibration as the cavity is filled. The dams are secured in position only long enough to limit the flow boundaries, then, after adjacent cavities are filled, the dams are quickly removed to facilitate structural bonding between freshly poured adjacent sections. Vertical, removable, re-useable pressure resisting dams are new elements for ICF construction, concrete construction trade work and related industries.